In organic electroluminescent (EL) elements, a charge-transporting thin film is used. Methods for forming the charge-transporting thin film are generally classified into dry process typified by the vapor deposition method and wet process represented by the spin coating method. These methods are appropriately used selectively, according to the area of the thin film to be formed and the solubility of the substance to be formed into the thin film in organic solvents.
In general, a layer called a hole injection layer and a layer called a hole transport layer are disposed between an anode and a light-emitting layer of an organic EL element, in this order from the anode side. The provision of these two layers makes it possible to enable efficient charge transfer, and to obtain an organic EL element which has high luminance characteristics (see, for example, Non-Patent Document 1). On the other hand, however, in the organic EL element production process, normally, there is a drawback that independent steps for forming each of these layers are needed.
In the field of electronic devices in recent years, simplification of process and simplification of element structure have been demanded, for the purpose of producing the elements in high yield and efficiently. Particularly, when a functional multilayer film in which a plurality of layers in an element are formed in a multilayer form is replaced by a single film, not only the production process can be simplified but also the element structure can be directly simplified. In view of this, in the field of various electronic devices, there is a demand for a material from which a functional single film capable of substituting an existing functional multilayer film can be produced. In the field of organic EL, also, there has been an increasing demand for a material which enables conversion of a functional multilayer film, composed of a hole injection layer and a hole transport layer as in a general structure, into a single film.